The protective circuit devices generally include a plurality of fuses so as to protect such a telephone equipment from power surges. In the event of such power surge, the fuses will become "blown" or open so that the connection between the power input line and the equipment to be protected is interrupted, thereby saving the equipment from damage. However, once the fuses have been "blown" there is required the time-consuming task of replacing the blown fuses with new fuses which can sometimes entail the rather difficult job of locating the "blown" fuses and inserting the new fuses into the telephone equipment.
Heretofore, it was known in the prior art to provide plug-in fuse structures for use with telephone terminal blocks so as to plug directly into the terminals thereof for protecting against surge currents. Examples of such plug-in fuse structures are disclosed in U.S. Pat. Nos. 4,800,465; 4,924,345; and 5,222,131.
U.S. Pat. No. 4,800,465 to E. W. Rodgers et al. issued on Jan. 24, 1989, discloses a mounting plate 34 for supporting one or more fuse blocks to a telephone equipment bay frame 20. The mounting plate is adapted to support one or more 8-pin fuse blocks 68, one or more 16-pin fuse blocks 104 or combinations thereof.
U.S. Pat. No. 4,924,345 to J. A. Siemon et al. issued on May 8, 1990, teaches a combined transient voltage and sneak current protector 10 which includes a two-piece substantially rectangular insulative housing 12. The housing has four spaced and aligned openings 30-36 at the bottom 38 thereof for receiving upstanding terminals from a terminal block. The interior of the housing is loaded with four contact members which are adapted to effect electrical connection with a three element surge suppressor and a pair of cylindrical fuse elements 62 and 64. The top surface of the housing 12 includes a handle 88 for assisting in its insertion into and retraction from the terminal block.
In U.S. Pat. No. 5,222,131 to R. H. Heidorn et al. issued on Jun. 22, 1993, and assigned to the same assignee of the present invention, there is disclosed a telephone protector 10 which is contained within a housing 12 having an input connection 36 and an output connection 38. The protector has an externally accessible fuse compartment 48 having fuse contact pairs. A removable fuse holder 14 is formed of substantially U-shaped cover member 74 bearing a plurality of fuse sockets 92. The cover member 74 is comprised of a base 78 and a pair of legs 80, each having a tang 70. The tangs are engageable with notches 68 formed in opposed panels of the housing so as to lock the cover member 74 onto the housing. The fuse holder 14 is capable of only holding a maximum of 8 or so fuses and thus can only be used to protect a limited number of electronic circuits.
In recent years, the telephone communication industry has demanded that relatively large multi-contact connectors be used for hard-wiring the incoming telephone lines and the telephone instrument station cables may include 25 wire-pairs. As is generally known in the art of telephone communication, there has been used extensively a certain connection block referred to sometimes as a "66-M type terminal connector block" that provides rapid wire installation of key telephone systems, PBX systems, cables and other low voltage terminal equipment. Typically, these 66-M type terminal blocks are mounted on a standoff bracket and serve as an interface with the user provided equipment. Further, the users are generally required to mount a connector(s) on the side(s) or bottom of the bracket so as to interface with the 66-M type terminal block. In FIG. 1, there is illustrated a conventional 66-M terminal block 2 of the prior art with a connector 4 connected to its one side and the figure has been labeled "Prior Art." These side connectors are frequently difficult to connect and disconnect from a plug 5 during installation and repair. In addition, if the protection devices were necessary, this required additional labor for installing the same to the 66-M type terminal block. These protection devices were generally specially-designed separate assemblies which had to be connected to the terminal block, that is, they were, plug-in type assemblies.
The present invention represents improvements over the conventional 66-M type terminal block used in telephone equipment and other communication applications as well as improvements over the above-discussed patents and in particular with respect to the '131 patent that could only protect a relatively small number of electronic circuits. In the present invention, the housing has been designed to fit into the same footprint as that of the conventional 66-M type terminal block. The printed circuit board is fixedly mounted internally of the housing and is adapted to receive a variety of different overvoltage and/or overcurrent protective circuit devices so as to provide the kind of electrical protection desired. Further, the housing is adapted to receive a plurality of first modular jacks connected to its exposed side and a plurality of second modular jacks connected to its protected side. Each of the plurality of first and second modular jacks is preferably of the type for a 4 wire-pair telephone line cord known as a RJ-45 jack so as to facilitate quick and easy mechanical connections to the protective circuit devices. A plurality of plug-in fuse modules are disposed in top recesses formed in the housing cover so as to protect the telephone communication related equipment and the like against a power surge. Each of the fuse modules is comprised of a fuse card holder and a miniature printed circuit board containing a plurality of fuses.